The invention relates to a hydrodynamic bearing the bearing element of which is arranged so as to be fixed against rotation and has at the inlet zone of its bearing surface a groove which is supplied with oil and is connected via an oil supply line to an oil pump. Bearing constructions of the general class to which the invention pertains are disclosed in U.S. Pat. Nos. 4,320,926 and 4,322,116.
The quantity of oil supplied to a friction bearing is planned according to the amount of heat which is generated in the bearing and is to be removed by the oil. This quantity of oil which is necessary for cooling purposes is always a multiple of the quantity of oil which is required by the bearing in order to produce the hydrodynamic lubricating film. Thus, the latter is drawn in automatically by the bearing from a surplus of oil while the remaining considerably greater quantity of oil is sprayed off in the proximity of the groove.
In known constructions a hydrostatic oil pressure (of 5 to 25 bars) builds up in this groove in operation, the level of the hydrostatic oil pressure depending on the one hand upon the size of the oil stream and on the other hand upon the present size of the gap between the bearing surface and the mounted element. If the gap is large then only a low oil pressure (inlet pressure) is produced; on the other hand, if the bearing surface and the mounted element match each other very well so that there is no significant air gap, then a high inlet pressure is produced in the groove.
The presence of inlet pressure of oil in the groove is desirable since it improves the drawing in of lubricating oil into the bearing and thus increases the reliability of the hydrodynamic lubrication. With increased operational reliability the bearing can be subjected to higher loads.
It is a disadvantage, however, that the level of the inlet pressure varies as a function of the clearances at the time and cannot be accurately predetermined. Therefore, the capacity of the oil pump must be planned for the maximum pressure which may occur. Thus, the known hydrodynamic bearings have the disadvantage that the oil pump must be designed for a very high degree of efficiency and in operation a large amount of energy is consumed by the quantity of oil which is sprayed off under high pressure and not drawn in to the bearing as a lubricating film. It is also a disadvantage that this quantity of oil which is sprayed from the groove does not ensure optimum removal of heat.